1. Field of the Invention
The present invention relates to a control unit for a construction machine, for controlling the operation of the working units of the construction machine, such as a hydraulic shovel.
2. Description of the Related Art
As is generally known, a hydraulic shovel, for example, is provided with a control unit having a single control lever pivotally supported for pivotal movement in longitudinal and transverse directions to facilitate the control of the working units of the hydraulic shovel. The control lever is shifted in logitudinal directions, namely, forward and backward directions, to control the arm and in transverse directions, namely, rightward and leftward directions, to control the bucket.
Such a known control unit will be described with reference to FIGS. 5 and 6. A control lever 1 is supported on a fixed lever stand, not shown, by a universal coupling mechanism 2 for pivotal movement in longitudinal and transverse directions. A bracket 3 is fastened to the lower end of the control lever 1 with a nut 4 pressing the bracket 3 against the lower end of the control lever 1 so as to pivot integrally with the control lever 1. When the nut 4 is loosened, the bracket 3 is allowed to turn about the axis of the control lever 1. The upper end of a first link rod 6 for operating a first hydraulic control valve 5 for controlling the operation of a first hydraulic cylinder actuator, for example, for operating the arm of a hydraulic shovel, and the upper end of a second link rod 8 for operating a second hydraulic control valve 7 for controlling the operation of a second hydraulic cylinder actuator, for example, for operating the bucket of the hydraulic shovel are joined to the bracket 3 respectively at positions spaced apart at an angular interval of 90.degree. in the circumferential direction. Only the first link rod 6 is pulled or pushed when the control lever 1 is shifted forward or backward to operate the first hydraulic control valve 5. Only the second link rod 8 is pulled or pushed when the control lever 1 is shifted rightward or leftward to operate the second hydraulic control valve 7.
In some cases, it is desired to change the setup of the control unit to change the mode of control operation; for example, from a mode of control operation to operate the bucket by shifting the control lever 1 in longitudinal directions to another mode of control operation to operate the arm by shifting the control lever 1 in the same directions. In such a case, the nut 4 is loosened to unfasten the bracket 3, the bracket 3 is turned through an angle of 90.degree. in a desired direction, and then the bracket 3 is fastened again to the control lever 1 with the nut 4. This method of changing the setup of the control unit requires a troublesome work for loosening the nut 4 with a spanner to unfasten the bracket 3 and for tightening the nut 4 with a spanner to fasten the bracket 3 again to the control lever 1.